079211 — Geosynthethic Stabilized Subgrade Using Graded Aggregate Base

211.01 Description

Furnish and place a layer of geotextile and 12 in. of graded aggregate base to bridge unstable material and minimize the use of undercutting. Use this item only when specified or directed. In extremely unstable areas, the Engineer may increase the thickness of the graded aggregate base material.

211.02 Materials

Graded Aggregate Base 901.01 Geotextile for Subgrade Stabilization-Class ST Section 919 Securing Pins or Staples 919.03

211.03 Construction

211.03.01 Test Strip. In extremely unstable areas, the Engineer may direct that a test strip be

constructed to determine the thickness of aggregate layer required to stabilize the area. The Engineer will determine the depth of aggregate to be used in the test strip. Construct the test strip at least 100 ft in length and at least one lane wide. The results of the test strip will be used to determine the thickness of aggregate required for subsequent construction.

211.03.02 Grade Preparation. Cut the area where the geotextile is to be placed to the depth

shown or as directed. Bring the area to the specified line, grade, and cross section. Provide a grade that is smooth as practical and free of debris. Minimize construction traffic on the grade. Remove ruts by reshaping, but do not overwork the grade. Have the grade approved prior to placement of the geotextile. Maintain adequate surface drainage as specified in 208.03.03. The Engineer may waive compaction and moisture requirements for the underlying soil. 211.03.03 Geotextile Placement. Place geotextile on the prepared surface for the full width of the area to be treated. In areas where longitudinal underdrain is to be placed, place the geotextile up to the edge of the proposed longitudinal underdrain trench, but not where the trench is to be excavated. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS Unroll the geotextile parallel to the base line. Do not drag the geotextile across the grade. Remove wrinkles and folds by stretching and pinning. Overlap the geotextile at least 30 in. at roll edges and ends. Overlap the end of the roll in the direction of aggregate placement, with the roll being covered by aggregate on top of the next roll. Pin all roll ends and roll end overlaps a maximum of 5 ft on center. Pin roll edges and roll edge overlaps a maximum of 50 ft on center. For curves, fold or cut the geotextile and overlap in the direction of the turn. Pin folds in the geotextile a maximum of 5 ft on center. Immediately repair or replace damaged geotextile as directed. Overlap geotextile patches at least 3 ft into undamaged geotextile. Do not allow traffic, including construction equipment, on the bare geotextile. 211.03.04 Aggregate Placement. Place the graded aggregate base as specified in Section 501, with the following exceptions:

211.04 Measurement and Payment

Geosynthetic Stabilized Subgrade Using Graded Aggregate Base will be measured and paid for at the Contract unit price per cubic yard. The payment will be full compensation for the test strip, and for all material, labor, equipment, tools, and incidentals necessary to complete the work. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS 212 — SUBGRADE DRAINAGE BLANKET CATEGORY 200 GRADING SECTION 212 — SUBGRADE DRAINAGE BLANKET

212.01 Description

Construct subgrade drainage blankets (SDB). Do not construct SDB in stormwater management (SWM) facilities or as drainage blankets for SWM facility embankments.

212.02 Materials

Graded Aggregate Base 901.01 No. 57 Aggregate 901.01 Securing Pins or Staples 919.03 Geotextile 919.01, Class SD Type II

212.03 Construction

212.03.01 Preparation. In the area where the SDB is to be placed, excavate 12 in. below the

elevation of the proposed bottom of the Graded Aggregate Base or as directed. If directed, adjust the depth or footprint of the SDB beyond the limits shown in the Contract Documents. Establish the grade to the line, grade, and cross section specified on the plans and to the satisfaction of the Engineer. Construct the grade as smooth as practical and free of debris. Minimize construction traffic on the grade. Remove ruts and reshape areas affected by construction traffic to the satisfaction of the Engineer. Do not overwork the grade to avoid causing further saturation or pumping of the subgrade. Maintain adequate surface drainage as specified in 208.03.03. Compaction and moisture requirements for the underlying soil on which the SDB is to be placed will be waived.

212.03.02 Geotextile Placement. Place a bottom layer of geotextile Class SD Type II on the

prepared surface prior to placement of 12 in. of No. 57 aggregate. Place a top layer of geotextile Class SD Type II after the No. 57 aggregate has been placed. Place the geotextile for the full width of the area to be treated. Unroll the geotextile on the grade parallel to the baseline. Do not drag the geotextile across the grade. Remove wrinkles and folds in the geotextile by stretching and pinning. Overlap the geotextile at roll edges and ends. Overlaps at the end of the roll are to be in the direction of aggregate placement with the previous roll on top. The minimum overlap is to be 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS